Concentrating liquid foods

ABSTRACT

Process and apparatus by which concentrated products produced at high pressures within a reverse osmosis concentrator may be withdrawn at a predetermined degree of concentration and without damage to their intrinsic properties even though they exhibit non-Newtonian properties. The invention is of particular importance in preparing concentrated products from liquid foods such as juices, lacteal fluids, egg white, etc.

United States Patent [72] Inventors EdisonLowe El Cerrito; Everett L.Durkee, El Sobrante, both of Calif.

[21] Appl. No. 8,114

[22] Filed Jan. 21, 1970 [45] Patented Jan. 11, 1972 [73] Assignee TheUnited States of America as represented by the Secretary of AgricultureOriginal application Feb. 18, 1969, Ser. No. 800,193, now Patent No.3,552,566. Divided and this application Jan. 21, 1970, Ser. No. 8,114

[54] CONCENTRATING LIQUID FOODS 2 Claims, 2 Drawing Figs.

[52] [1.8. CI 99/199, 99/28, 99/31, 99/45, 99/55, 99/105, 99/113 [51 1Int. Cl A23b 7/02 [50] Field of Search 99/ 199,

[56] References Cited UNITED STATES PATENTS 1,825,631 9/1931 Horvath210/23 3,423,310 1/1969 Popper 210/23 OTHER REFERENCES Morgan et al.,Reverse Osmosis. Food Technology. Dec. 1965 (pages 52- 54).

Primary Examiner-Lionel M. Shapiro Assistant ExaminerD. M. NaffAttorneysR. Hoffman, W. Bier and W. Takacs PATENTEBJANI 1 1912 3,634,103

RESERVOIR REvERsE E3 WATER OSMOSIS F ,UNIT 4 g; -L|QUID LEVEL SWITCHF/G.

1 6 JCONCENTRATE WATER TO DRAIN MICRO SWITCH WATER 4 l6 MAIN 6 Jr 29 25CONCENTRATE (PRODUCT) I WATER TO DRAIN POWER '4 sEo. SUPPLY 7 MOTORMICRO- SWITCH mum F G 2 LEVEL SWITCH A BWK.

ATTORNEYS CONCENTRATING LIQUID FOODS This is a division of ourapplication, Ser. No. 800,193, filed Feb. 18, 1969, now US. Pat No.3,552,566, issued Jan. 5, 1971.

A nonexclusive, irrevocable, royalty-free license in the inventionherein described, throughout the world for all purposes of the UnitedStates Government, with the power to grant sublicenses for suchpurposes, is hereby granted to the Government of the United States ofAmerica.

DESCRIPTION OF THE INVENTION The invention relates in general to the artof concentrating liquids by reverse osmosis. More particularly, theinvention is concerned with and has among its objects the provision ofnovel apparatus and process for controlling the degree of concentrationattained in reverse osmosis operations, and for discharging concentratedproduct from such operations without damage to the product. Furtherobject of the invention will be evident from the following description.

Unless otherwise specified, degrees of concentration referred to hereinare by volume. For example, if 100 volumes of starting liquid is reducedto 50 volumes by elimination of 50 volumes of water, the product may betermed a twofold concentrate; if the same original volume of liquid isreduced to 33% volumes, one will have a threefold concentrate; and soon. The rate of flow of liquids is also herein referred to on a volumebasis.

In recent years it has been shown that reverse osmosis is useful forconcentrating various liquid foods such as fruit juices, vegetablejuices, milk, egg white, and the like. See, for example, Lowe andDurkee, US. Pat. No. 3,341,024, and Popper, US. Pat. No. 3,423,310. Inconducting reverse osmosis the liquid to be concentrated is appliedunder superatmospheric pressure against a suitable membrane. Water (fromthe liquid) passes through the membrane, leaving a residue ofconcentrated liquid on the upstream side of the membrane. The permeate(water) and concentrate are separately discharged from the system.

In conducting reverse osmosis operations, various problems areencountered. One involves the matter of controlling the degree ofconcentration achieved. For example, the operator may require a productof twofold concentration or one fourfold concentration, etc., dependingon particular circumstances. It might be thought that such control couldbe attained by providing a valve in the concentrate discharge line tothrottle the rate of discharge-for example, if a twofold product isdesired, to crack the valve to such a degree that the rate of dischargeof concentrate is one-half the rate of inflow of starting liquid. Such atechnique, however, is completely inoperative, primarily because of theintrinsic properties of the liquids being handled. Virtually all liquidfood products such as fruit and vegetable juices; milk, whey, and otherlacteal fluids; egg white and other egg liquids; etc. are non-Newtonian.That is, the viscosity of these liquids is a function of the shear ratethat is imposed on the liquid. The higher the shear rate, the lower theviscosity of the liquid, and vice versa. This, of course, is in sharpcontrast to Newtonian liquids (water or aqueous salt solutions, e.g.) inwhich case viscosity does not change with rate of shear. Consequently,in handling liquid food products, if throttling is applied to theconcentrate discharge line, the system will operate erratically. Forexample, if the valve is just barely cracked the rate of shear will below, viscosity will be high, and the flow will decrease or ceasecompletely. If then the valve is opened further, the shear rate willincrease with resulting decrease in viscosity and the liquid will pourout at an excessive rate. Readjustment of the valve will simply startthe cycle again with the flow in any valve position being completelyunpredictable and unstable.

A primary object of the invention is the provision of means forobviating the problem outlined above. By applying the principles of theinvention one is enabled to readily control the degree of concentrationattained in reverse osmosis procedures, even where the liquid beingtreated is non-Newtonian.

Another problem in reverse osmosis concentrations is the matter ofdamage to the product. If the products are released directly from thehigh pressure environment of the reverse osmosis equipment, orespecially if they are released through a throttling device, they aresubjected to extreme shear stresses which cause irreversible changes intheir properties. A typical case in this regard is egg white. Egg whiteis especially valuable in the baking industries for its aerationproperties. If, however, egg white is subjected to high shear stressesas in passing directly, or with throttling action, from a high pressurezone to one at atmospheric pressure, its aeration properties aresubstantially impaired. One of the prime objects of the invention is theprovision of means for alleviating this problem. Thus, by application ofthe principles described herein one is able to withdraw concentratedproducts from the reverse osmosis system while retaining the originalproperties thereof, including the aeration properties of egg products.

The manner in which the aforesaid objects and advantages are attained isnext described in detail, having reference to the annexed drawing,wherein:

FIG. 1 is a diagrammatic view of apparatus in accordance with theinvention. To avoid confusion with the mechanical parts, electricalconnections have been omitted.

FIG. 2 is a wiring diagram illustrating the connections of the variouselectrical components of the apparatus of FIG. ll.

Referring now to FIG. 1, the liquid to be concentrated-egg white, forexampleis held in reservoir 1.

The egg white is forced under superatmospheric pressure by pump 2 intothe reverse osmosis concentrator represented by block 3. This latterdevice may embody any of the known devices such as that of Lowe andDurkee, US. Pat. No. 3,341 ,024. The particular structure of the reverseosmosis unit forms no part of the present invention.

Reverse osmosis unit 3 is provided with pipe 4 for discharge of water(permeate), and pipe 5 for discharge of the concentrated product. Itwill, of course, be understood by those skilled in the art that theconcentrated product leaving unit 3 is under superatmospheric pressure,typically on the order of about to about 2,000 p.s.i.g.

The illustrated apparatus includes an automatic syphon, generallydesignated as 6. This syphon meters the outflow of water (permeate) fromreverse osmosis unit 3, and also cooperates with a discharge meteringunit (hereinafter described) to correlate the discharge of concentratewith the discharge of water (permeate), thereby providing means forcontrolling the degree of concentration attained in the reverse osmosisconcentration. Details on the construction and operation of syphon 6 areprovided below.

Syphon 6 includes an open-topped container 7 and a discharge pipe 8. Thewater leaving unit 3 via pipe 4 flows into container 7. When the watercollecting in container 7 rises to the level indicated, syphon actiontakes over and the container is quickly emptied via pipe 8. Duringoperation of the system, container 7 is repeatedly filled and emptied bythis syphon action.

A liquid-level switch 9 (which may take the form of a 0 current relay,for example) is provided near the top of container 7. Each time thewater level rises to the point that syphon action takes over, switch 9is actuated and it in turn actuates sequential motor 13 as hereinafterexplained.

Reference numeral 11 designates a rotary ball valve operated throughshaft 12 by motor 13. This motor is of the sequential type, that is,when it is energized (by liquid-level switch 9 or by microswitch 14) itwill rotate and come to a dead stop. Thus, when motor 13 is energized byliquid-level switch 9 it rotates valve ill to the position shown in FIG.I, that is, with communication between pipe 5 and pipe 15. Whenenergized by microswitch 14, motor 13 rotates valve 1] 180 so that thereis communication between pipe 15 and pipe 16.

For controlling the discharge of concentrate in cooperation with syphon6, there is provided a concentrate metering unit generally designated as10. This unit includes baseplate 17 on which is mounted cylinder 18. Afree piston 19 subdivides cylinder 18 into compartments 20 and 21.Attached to piston 19 is a piston rod 22 which passes (via aconventional gland or seal, not illustrated) to the exterior of cylinder18. Microswitch 14 is mounted on threaded rod 23 so that the position ofswitch 14 can be adjusted for particular conditions. In operation,microswitch 14 cooperates with piston rod 22 as hereinafter explained.

At its right end cylinder 18 communicates with pipe 15, at its left endwith pipe 24 equipped with needle valve (adjustable orifice) 25. Abranch pipe 26 equipped with check valve 28 is connected to main 29which provides a supply of water under usual house pressure, e.g., about35-75 p.s.i.g. During operation, compartment 20 is kept full of water atthe pressure supplied by main 29. Needle valve permits the discharge ofexcess water from compartment 20 as piston 19 traverses to the left,while maintaining the desired back pressure of water in compartment 20.Check valve 28 prevents water from backing up into the house line. Avalve 30 is also included in the system so that one may control the rateat which water from main 29 will enter pipe 26 and other units connectedtherewith. During the operation, valve 30 remains in a set position.

The operation of the controlled discharge system is explained asfollows:

As the action in reverse osmosis unit 3 takes place, water (permeate) isdischarged into cylinder 7. When the water level rises to contact switch9, motor 13 is triggered to rotate valve 11 to the position shown inFIG. 1. This allows concentrate to flow into compartment 21 where itmeets the resistance offered by the water present in compartment 20. Theconcentrate being at higher pressure, forces piston 19 to the left andthis, in turn, forces excess water out of the system via needle valve25, this valve having been preset to provide a small orifice. Byproviding a back pressure of water in this manner the concentrate isgradually removed from the reverse osmosis unit 3 without subjecting itto excessive stress. At the same time a metering effect is attained.Thus, when piston rod 22 moves far enough to the left to contactmicroswitch 14, valve 1 l is rotated to a second position whereby flowof concentrate into compartment 21 ceases. Instead, compartment 21 isnow in communication with product discharge pipe 16. Since the end ofthis pipe is open to the atmosphere, the concentrate in compartment 21is instantly depressurized. The concentrated product is, however, notdamaged because there is no flow i.e., the product is not subjected toshear forces. It is thus a significant advantage of the invention thatthe concentrated product is depressurized while in a static condition,whereby the pressure reduction is achieved without damage to itsproperties. After the abovedescribed depressurization takes place, thepressure on the left side of piston 19 is the higher and consequentlythe influx of water through pipe 24 forces the concentrate fromcompartment 21 via valve 11 and pipe 16 out of the system. The rate atwhich the concentrate is discharged depends on the setting of valve 30.In typical operations, this valve is set so that the concentrate isdischarged gradually, rather than in a sudden burst, whereby to avoidsubjecting it to undue stresses.

Meanwhile, of course, additional water (permeate) has been flowing intocontainer 7 and when the level of water reaches switch 9 the dischargecycle commences again.

The following explanation illustrates how the system may be adjusted tosecure a desired degree of concentration.

If, for example, it is desired to obtain a twofold concentrate oneproceeds as follows: The position of microswitch 14 is so set thatpiston rod 22 contacts this switch when compartment 21 takes on the samevolume as the effective volume of container 7. (By effective volume ismeant the volume of container 7 considered from its base up to the levelat which syphon action takes over.) In this way one obtains one volumeof concentrate per volume of water removed from the starting liquid. If,on the other hand, a more highly concentrated product is desired, onewould adjust the position of microswitch 14 so that it is contacted bypiston rod 20 when the volume of compartment 21 is a predeterminedfraction of the effective volume of container 7. For example, if thesetting of rod 23 is such that the switch 14 is triggered whencompartment 21 has a volume one-half of the effective volume ofcontainer 7, one will achieve a 2/1 concentration, or, expressed inother terms, a threefold concentrate.

As explained above, in the system of the invention the discharge ofconcentrate is controlled by metering the discharge of permeate. Thissystem not only provides the desired result that the ratio ofconcentration can be set and maintained at any desired level, but alsoprovides additional advantages of simplicity and economy. These latteradvantages stem from the fact that the penneate is discharged from thereverse osmosis concentrator at essentially atmospheric pressure. Hencethe metering of this liquid, the permeate, can be done with simple andinexpensive equipment, such as the syphon arrangement shown in FIG. 1.

This invention is of wide applicability and can be used for theconcentration of liquid foods of all kinds. Typical liquids to which theinvention may be applied are listed below solely by way of example andnot limitation:

Fruit and Vegetable Products: Juices, extracts, pulps, purees, andsimilar liquid products derived from fruits or vegetables such asorange, grapefruit, lemon, lime, apple, pear, apricot, strawberry,raspbeny, cranberry, pineapple, grape, prune, plum, peach, cherry,tomato, celery, carrot, spinach, onion, lettuce, cabbage, potato,sweetpotato, watercress, etc. The liquid products may be prepared incustomary manner by subjecting edible portions of the produce to suchoperations as reaming, pressing, macerating, crushing, comminuting,extracting with water, cooking, steaming, etc. These operations may beapplied to the fresh produce or to processed produce, that is, producewhich has been subjected to such operations as cooking, blanching,freezing, canning, sundrying, sulphiting, or preservation by applicationof chemical preservatives or ionizing radiations.

Meat and Fish Products: Meat extracts, meat juices, soups or broths madefrom meat or fish products with or without added vegetative material,clam juice, oyster stew, fish or clam chowders, etc.

Lacteal Products: Whole milk, skim milk, whey, cream, buttermilk,yogurt, milk products containing such additives as chocolate, cocoa,sugar, malt, vitamins, sugar, etc.

Cereal Products: Aqueous extracts of cereals such as wheat, barley,malted barley, rice, corn, etc.

Beverages: Aqueous extracts of coffee, tea, chocolate, yerba mate,roasted cereal products (simulated coffee products), etc.

Carbohydrate Substances: Honey, maple syrup, corn syrup, sorghum syrup,molasses, etc.

Egg Products; Egg white, egg yolk, whole egg, or preparations of eg withother foods such as milk, cream, sugar, flavorings, etc.

Miscellaneous: Juices, extracts, purees and other liquid products madefrom alfalfa, clover, grasses, cottonseed or soybean meals, sugar cane,sugar beet, sorghum, animal blood, etc. Vitamin preparations such assolutions of ascorbic acid, thiamin or other vitamins, vitaminconcentrates or precursors, fermentation products such as beers (cultureliquors) containing mushroom mycelium, yeasts, biosynthesized vitamins,etc.

Having thus described the invention, what is claimed is:

1. A process for concentrating a liquid food by reverse osmosis whichcomprises:

a. pumping the liquid food under superatmospheric pressure into areverse osmosis concentrator to provide an effluent stream of permeatewater and a separate effluent stream of concentrate undersuperatmospheric pressure,

b. discharging the stream of permeate water from the coneentrator,

c. flowing the stream of concentrate from the concentrator into adepressurizing zone isolated from the concentrator,

d. in the depressurizing zone reducing the pressure on the concentratewhile it is in a static condition, and

c. removing the said stream of concentrate from the concentrator at arate proportionate to the rate of discharge of water,

d. conveying the stream of concentrate to a zone isolated from saidconcentrator, and

e. in said isolated zone depressurizing the concentrate while it is in astatic condition.

2. A process for concentrating a liquid food by reverse osmosis whichcomprises: a. pumping the liquid food under superatmospheric pressureinto a reverse osmosis concentrator to provide an effluent stream ofwater and a separate effluent stream of concentrate undersuperatmospheric pressure, b. metering the said stream of water as itdischarges from said concentrator, c. removing the said stream ofconcentrate from the concentrator at a rate proportionate to the rate ofdischarge of water, d. conveying the stream of concentrate to a zoneisolated from said concentrator, and e. in said isolated zonedepressurizing the concentrate while it is in a static condition.